The present invention relates to machines for surfacing of workpieces, such as ingots, electrodes, billets or bars, for use in the metallurgical industry and more particularly to an apparatus for abrasive machining of workpieces.
Apparatus for abrasive machining or workpieces of various designs are known in the art as exemplified by U.S. Pat. No. 2,142,736 /Cl. 90-18/, wherein there is provided an apparatus comprising a tool made fast on a spindle, the axis of which is perpendicular to the surface of a slab to be machined, a tool head with the spindle mounted on a bed and, also mounted on the bed, two drive means, viz. a traverse feed motor and a tool driving motor, the latter of which is connected to the spindle through a V-type belt.
In the course of machining the tool is initially positioned for removing a layer of selected thickness and thereafter the tool driving motor is engaged for surfacing the slab while the latter is being fed perpendicularly in relation to the axis of the spindle. However, this apparatus fails to provide the tracing of the tool over the curves of the surface being machined and therefore fails to ensure a uniform scalping or removal of metal along the entire length of the slab because the tool head is rigidly secured to the bed and is incapable of axial movement during slab machining.
Another prior art apparatus intended for abrasive machining of billets/cf. British Pat. No. 995,125, Cl. B3 D, published 1965provides a tool carrier supporting a grinding wheel made fast on a spindle. The carrier is pivotally connected to a bed through a rocker-arm, a tool drive means is arranged on the carrier, a traverse feed drive means, and an actuating hydraulic cylinder for urging the tool to the billet surface being machined. The cylinder is pivotally connected to the bed and the tool carrier. In the course of machining the actuating hydraulic cylinder acts to urge the tool to the billet, whereas the tool oscillation transversely of the continuous advancement of the workpiece is effected by a rocker-arm drive. However, this apparatus also fails to ensure metal scalping of a uniform thickness due to the fact that the traverse feed drive mechanism is incapable of providing a steady cutting engagement of the tool with a workpiece being machined.
The use of more powerful drive means for grinding tools leads to an increase in the bulk of tool heads, thus lowering the frequency of the reciprocating motion thereof across the workpiece being machined owing to greater dynamic loads which results in deteriorated quality and reduced efficiency of machining.
In still another known apparatus for abrasive machining /cf. GDR Pat. No. 26,927, Cl. 67a/3, published 1964/ which is the closest analogue of the present invention, the rod of an actuating cylinder is pivotally connected to one link of an articulated four-bar linkage, the link is shaped as a two arms lever carrying a counterweight acting to balance an abrasive tool. The rod cooperates with the two arms lever through a shackle having a slidable provision for a slide block. The above apparatus is not free of disadvantages in that tracing of the tool over the surface being machined is done in only one direction from the original setting of the tool, thereby leaving unsurfaced cavities on the workpiece being machined. Also, a bulky tool drive means in conjunction with the counter-weight adds to the forces of inertia, which complicate the tracing of the tool over the workpiece surface.
The heretofore described apparatus along with numerous other machines are incapable of affecting mass production abrasive machining of high efficiency, since recent advances in the art of abrasive machining have evidenced a steady increase in the rate of cutting speeds and specific forces acting to urge a tool to a workpiece, which are difficult to realize in conventional abrasive machines. In this connection, problems arise in the designing of circular grinding machines having wheel rotation speeds of up to 100-14 120 m/s, reliable spindle bearings and drive-to-spindle power transmissions.